This invention relates to novel starch sulfomaleate half-esters and to a method for their preparation. It also relates to modified starch sulfomaleate derivatives which contain other substituent groups on the starch base. It further relates to novel starch disulfosuccinate half-esters and their preparation.
Starch esters containing sulfonyl groups, including the sulfosuccinates, have been prepared by treating granular starch in an aqueous suspension with the cyclic dibasic acid anhydrides of ethyleneically unsaturated organic acids (e.g. maleic, citraconic, itaconic, and crotonic acid) and treating the resulting unsaturated starch half-esters with sodium, potassium, or ammonium bisulfite to form the saturated half-esters containing sulfonyl groups by addition across the double bond (see U.S. Pat. No. 2,825,727 issued Mar. 4, 1958 to C. G. Caldwell). Amphoteric sulfosuccinates of fluidity starches have been used as pigment retention aids in high alum systems (see U.S. Pat. No. 4,029,544 issued June 14, 1977 to W. Jarowenko et al.). They are prepared using the general procedure of the Caldwell patent, i.e. a granular fluidity starch base (4-40 W.F.) containing cationic or cationogenic substituent groups is reacted with maleic anhydride to form the starch succinate and then with a bisulfite to form the sulfosuccinate. In addition to the controlled amounts of cationic quaternary ammonium ether groups or cationogenic aminoalkyl ether groups and sulfosuccinate groups, the derivatives may contain other substituent groups such as phosphate, hydroxypropyl, or acetate groups.
As used herein, the term "amphoteric" starch derivatives refers to starch derivatives where anionic and cationic (or cationogenic) groups are bonded to the same or to different reaction sites on the starch molecule through a zwitterionic substituent group or through separate anionic and cationic (or cationogenic) substituent groups. The term "cationic" groups is hereafter intended to include cationogenic groups, which are nonionic substituent groups capable of forming cations (e.g. diethylaminoethyl ether groups).
The present invention provides novel starch sulfomaleate half-esters and a method for their preparation. It also provides modified starch sulfomaleate derivatives which contain other substituent groups. It further provides novel starch disulfosuccinate half-esters prepared by reacting the starch sulfomaleate with a bisulfite.